This invention relates generally to polymer memories.
In polymer memories, the polarization of a polymer may be altered by changing the voltage applied across that polymer. An array of row and column or bit lines may be arranged transversely to one another with polymer material between those rows and columns at each row line/column line intersection. The intersection of each row and column defines a single memory element, or “pixel.” Any number of stacks of polymer memory layers may be combined to increase the memory capacity. Polymer memories are also called thin film electronics memory and polymer ferroelectric random access memory.
Generally, the polarization of the memory pixel is achieved upon the application of an appropriate voltage. In the course of writing to a given location, however, unaddressed bits on the same bit or column line experience a voltage that is less than the normal voltage used to achieve the desired polarization of a pixel. This voltage is called the write disturb voltage. The disturb voltage may be of either positive or negative polarity.
For a small number of applied disturb voltage occurrences, due to a small number of write sequences, an unaddressed pixel retains nearly all of its intended polarization. However, if a large number of writes occur that affect the same unaddressed bit, and if those writes all have the same polarity, the polarization of an unaddressed bit can be reduced to the point where its content is corrupted. This may result in a bit error.
The problem is aggravated in polymer memories because polymer memory read operations are destructive. As a result, after each read operation, the data is written back to the same location. As a side effect of these repeated writes after each read, adjacent bits on the same bit lines in the array may experience disturb voltages. The polarity of the disturbed voltage is determined by the value of the bit being written on the associated bit line. If an address is read many times, the data must be written back an equal number of times, all with the same polarity. The cumulative effect of these write disturbs may degrade noise margin at other locations.
Thus, there is a need for a way to reduce the write disturb problem in polymer memories.